Serena Williams opened up Monday after her historic defeat at a San Jose tournament last week.

"Last week was not easy for me," she wrote in an Instagram post. "Not only was I accepting some tough personal stuff, but I just was in a funk. Mostly, I felt like I was not a good mom."

The 23-time Grand Slam champion implied she was suffering from "postpartum emotions." Conversations with the women in her life helped her realize "it's totally normal to feel like I'm not doing enough for my baby," she wrote.